io8 Biological Chemistry. 



Amides can also be prepared in fact, each carboxyl group 

 exhibits the properties characteristic of that group. 



Oxalic acid, which separates from aqueous solutions in 

 crystalline form with two molecules of water of crystal- 

 lization (C0 2 H) 2 2H 2 1 , is produced by the oxidation of a 

 large number of organic substances, and is prepared on a 

 large scale by heating sawdust with a concentrated solu- 

 tion of sodium hydroxide to 240 in iron pans. From the 

 extract of the melt it can be precipitated by calcium salts, 

 as calcium oxalate, C 2 O 4 Ca H 2 O (one molecule of water of 

 crystallization), is practically insoluble in water. Oxalic 

 acid is readily oxidized, and is used extensively on this 

 account in analytical chemistry ; thus, in the presence of 

 warm potassium permanganate, it is oxidized to carbon 

 dioxide and water 



COOH 



| + = 2C0 2 + H,0 



COOH 



As the crystalline substance can be readily obtained in a 

 state of great purity, it is a convenient substance to 

 employ for the standardization of permanganate solutions. 

 Oxalic acid is largely used for various technological pur- 

 poses. 



/COOH 

 Malonic Acid, CH 2 , is an important substance 



\COOH 



on account of the employment of some of its derivatives 

 in chemical synthesis. On heating, it decomposes into 

 acetic acid and carbon dioxide. This reaction is typical of 

 substances in which two carboxyl groups are attached to 

 the same carbon atom 



/COOH 



CH 2 =CH 3 COOH 

 \COOH 



